A small bug in preferences

After setting the 'default startup' in preferences, the okay button doesn't light up. The only option is to push the cancel button. It works to set the default startup but it doesn't seem to be consistent behaviour for the user interface. This is reproducible on my two machines.

Right now the reason it does not activate the OK is that when you click to save a new session you are not actually making a change to the preferences, just saving a new startup session to the disk. We can change this for the next rev, so that it does activate the OK, but it will still not make a difference which button you click, both OK and Cancel will dismiss the dialog (unless there are other changes) but the session is already saved.